Apparatus for truing grinding wheels



March 14, 1944.

| TURRETTINI APPARA'I'LTS FOR TRUING GRINDING WHEELS Filed Sept. 10. 1943 3 Sheets-Sheet 2 T a A lair/.5

Ma'rch 14, 1944.

Filed Sept. 10. 19,43

3 Sheets-Sheet 3 J .H g. Q 8 .Nb q E 3 ow $1 M mm 9 MW q I I I 3 3 v Qb/ v i E/ QN E :w 3 N w n g mm mw $6 1% a a mm D u mm 2 Q n4 n1 3 v In, van/flier T'Turr e-Z-Z z'zz v I. V 0 V/////////// Patented Mar. 14, 1944 APPARATUS FOR TRUING GRINDING WHEELS Fernand Turrettini, Geneva, Switzerland, assignor to the firm Societe Genevoise dlnstruments de Physique, Geneva, Switzerland, a firm of Switzerland Application September 10, 1943, Serial No. 501,858 In Switzerland October 2, 1942 8 Claims. (01. 125-41) The object of the present invention is an apparatus for truing a grinding wheel. This apparatus is characterized by a shaft mounted in its bearings in such a way as to be able to rotate and to slide axially, the axis'of this'shaft being intended to occupy in relation to the grinding wheel the same relative position as the axis of the piece to be ground, by a diamond carried by the shaft and mounted in such a way as to be able to slide parallel with the sides of this grinding wheel, by a supsmathe slope of the supporting plane, the whole in such a way that when one operates the shaft and the diamond, the latter describes a portion of helicoid corresponding to that part of the thread to be dressed which comes in contact with the grinding wheel, the pitch of this helicoid being determined by the inclination of the supporting plane.

' The attached drawings represent, by way of example, an embodiment of the object of the present invention.

Fig. 1 is a plan view, the embodiment being mounted on the table of a machine for dressing the threads by grinding.

Fig. 2 is a horizontal section through the axis X-'-X of the embodiment and through the centre of the grinding wheel.

Fig. 3 is a transverse section through III-III and Fig. 4 a transverse section through IV-IV of Fig. 2. r

Fig. 5 is a longitudinal section through V'V of Fig. 2 and Fig. 6 is a transverse section through VI-VI of Fig. 5.

Fig. '7 is a reproduction in larger scale of a part of Fig. 2.

In Fig. 1, 8i is the sliding table of the grinding machine, which table can move rectilineally in front of the grinding wheel I. This table carries the fast head stock 82 and the adjustable head stock 83 between th points of which can be placed the workpiece 84 to be dressed by grinding. Beyond the adjustable head stock 83 is the truing apparatus, fixed on the table by its casing 11 and shown in detail in Figs. 2 to 6.

When dressing the thread ofthe piece 84, the

position of the table is such, that this piece is facing the grinding wheel. This piece revolves on itself whereas the table moves in front of the grinding wheel, which revolves also on itself. For truing the grinding wheel, one moves the table 8I until it comes to abut against the fixed stop 85. In this position, the diamond 2 of the truing apparatus is in position in relation with the grinding wheel for truing it; the axis XX of the truing apparatus, axis which is in the prolongation of that of the piece 84, then occupies the same position as was previously occupied by the axis of the piece 84.

In Figs. 2 to 6, I is the grinding wheel and 2 the diamond. The latter is mounted in a diamond holder 3 fixed in a head 4 pinned at the end of a slider 5. This slider is of circular section except in the portion comprised between its shoulders 6 and 7, in which it is cut as a rack 8 engaging a pinion 9, the axis I0 of which coincides with that of the pivot II of the revolvable turret I2; the rotation of this turret permits to adjust at the required value the angle comprised between the middle plane of the grinding wheel and the trajectory of the diamond.

The slider 5 is guided, on th side of the diamond, by the bearing I3, and at the rear by the shoulders 6 and I. A protecting cap I4 of the head 4 prevents the grindin dust from getting into the bearing I3. The shoulder I presents a slot I5 in which engages a prismatic guide I6 solid with a cover I! which closes the recess of the slider towards the rear. The guide l6 prevents the slider from revolving on itself.

The revolving turret I2, after having been adjusted at the required angle by means of a graduation not shown traced on its periphery, can be immobilised by a clamping screw I8 operated by the handle I9. The shaft It is provided with a handle 20, respectively 20, at each one of its ends, in order that one of them remains accessible in all positions of the turret I2. The latter turns by its pivot II in a bearing 2i of a shaft 22 mounted rotatively in a support 23.

The shaft 22 carries at the rear a head 24 pro- .vided with a spring pointer 25 which can engage into one or the other of two recesses 26 disposed at from one another. If one rotates the shaft 22 by half-a-turn with all the pieces it carries, the slider 5 will take a position in symmetry with that which is shown, inv which new position the diamond will true the other side of the grinding wheel without any new angle adjustment.

The support 23 can move in a slide 21 in dovetail (see Fig. 5) cut in an arm 28; th position of the support 23 along the arm 28 is adjustable with the help of a screw 29 according to the surface of abutment T! of the casing H;

diameter of the helicod to be ground. A sheet metal cover solid with the support 23 protects the dovetail against dirt. The arm 28 is screwed on the end of a shaft 3| which can slide and revolve in bearings 32 and 33, being constantly pressed from left to right by a helical spring 34 leaning on one side on a thrust ball-bearing 35 and on the other side on a nut 36; the bearings 32 and 33 are fixed to the casing 11 and the axis X-X of the shaft 3| is the same as that XX of the Fig. 1.

The shaft 3| carries at its inner end a gear 3'! engaging a pinion 33 able to rotate around a shaft 33 set on one side in the piece 40 fixed to the casing and on the other side in a ring 4| screwed on the piece 43. The latter is crossed through and through by a wide aperture 42 which lets subsist to the left, in Fig. 1, the bosses 43, 44 and 45 (see also Fig. 4) which are united at their end by the ring 4|. The pinion 38 engages with a rack 46 cut in the slider 41 Which moves in two slides 43 and 43' provided in the bosses 43, 44 and. 45. The slider 41 is guided in these slides 48 and 48 by its heels 49 and 50 as well as 5| and 52.

The slider 41 carries (see Figs. 2, 4 and 5) two forks 5354 and 55-56 in which slide two hubs 51 carrying the ends of a shaft 58, the axis of which is at right angle to that of the shaft 3|. This arrangement enables the shaft 58 to get away from, or closer to the slider 41 under the action of the inclined plane 59 and 59' on which vrest the ball-bearings 60 and 60 mounted on the shaft 58. The latter carries, in its middle part, a ball-bearing 6| resting against the rectangular head 32 of a pivot 63 lodged in the shaft 3|.

The thrust of the spring 34 thus passes from the chain of the following pieces: nut 36, shaft 3|, pivot 63, its head 62, shaft 58, ball-bearing 6|, ball-bearings 60 and 60' and reports itself on the inclined plane 59 and 59' which is provided in a piece 64 turning on the pivots 65 and 65 set in the piece 40.

The piece 64 can form an adjustable angle with the axis of the shaft 3|, because it presents at the rear also a fork 66 and 66' which embraces a die 61 pivoted on a shaft 68 solid with a slider 69 moving in a rectangular slide 10 under the action of an adjusting screw 1 I, which is provided with a head l2 possessing a graduation.

On an annular surface 15 ofthe casing T1 can revolve the ring 14 crossed by the screw '13, the upper end of which carries acontrol head 16 and the lower end of which l6 rests on a The ring 14 carries an arm 80 serving as bearing to a roller 19, on which rests a rib 28' of the arm 28; this rib is maintained constantly in contact with the roller by the weight of the arm 28. By screwing or unscrewing, in the ring 14, the screw 13, the lower end of which still rests on the casing, one causes this ring 74 to rotate around the axis XX of the shaft 3| and, consequently, also the arm 28 resting on it and the shaft 3| fixed on this arm. This movement of rotation communicates itself through the gear 37, the pinion 38 and the rack 45, to the slider M, which moves in its slide at right angle to the axis of the shaft 3 This transverse motion communicates itself through the forks 53-54 and 55-56 to the shaft 58, which then displaces itself parallel to the inclination of the inclined plane 59 and 53';

If this inclined plane finds itself at right angle to the axis of the shaft 3|, as showninFig.

1, it will itself be parallel to the end of the rectangular head 62 and the transverse displacement of the axis 58 will remain without influence on the axial position of the shaft 3|.

If on the contrary, as shown on Fig. 4, the inclined plane makes for instance an angle of 45 with the axis of the shaft 3|; the head 62 resting constantly on the ball-bearing iii, the ball-bearing 60 and 63' resting constantly on the inclined plane 59 and 59, the head 62 will incur an axial displacement equal to the amplitude of the transverse displacement of the shaft 58. The axial displacement of the head 32 communicating itself to the shaft 3|, one sees that this shaft will turn and slide simultaneously, in such a way as to describe, together with the arm 28 and the pieces which it carries, an helicoidal trajectory, the pitch of which will be equal to the development of the gear 3'! multiplied by the tangent of the angle b formed between the axis of the piece 3| and the axis of the fork 66 and 66'. The value of this tangent is directly measurableby a graduation provided on the divided head 62 and on the scale 18.

One can thus by a suitable adjustment of the value of the tangent b, to be read directly on the above mentioned elements, cause the shaft 3| and consequently the diamond 32 to describe an helicoidal trajectory of predetermined pitch, the value of which will always be equal to the pitch of the helicoid to be ground.

The utilisation of the apparatus will be as follows:

Having adjusted the angle a at the value suit able for the piece to be dressed and the angle b in accordance with the pitch of the piece to be dressed, the arm 28 being in horizontal position, one acts on one of the handles 20 and 20' which control the movement of the diamond along the side of the grinding Wheel, causing this diamond to move alternatively and to cut a generatingline of the side of the grinding wheel, and then by operating on the screw 73, one places the arm 28 in a position slightly oblique in respect to the horizontal, whilst one continues to operate on the diamond. Proceeding in this way step by step, one explores with the point of the diamond the enveloping surface of the helicoid to be dressed as far as the top where the die.- mond will not touch any more the grinding wheel. At this moment, one will turn the pivot 22 by half-a-turn on itself for presenting the diamond on the opposite side of the grinding wheel, which one will cut by the same process. During these operations the grinding wheel rotates naturally at high speed.

This device thus permits to out a grinding wheel for very steep pitches by causing the diamond that cuts the grinding wheel to explore the enveloping surface of the helicoid to be dressed and by producing this h'eli'cal movement by the operation of the device, the table of the grinding machine standing still at this moment.

The above described truing apparatus sesses great advantages especially for t'ruing in a practical way a grinding wheel intended for dressing threads with very steep pitches and which consequently must be strongly inclined for fitting a fillet of high pitch.

One knows that when the sides of a grinding wheel which must dress a fillet of high pitch are cut with r'ectilineal generating lines, in order to form a revolution on'e, they will not produce on the piece-to be wrought a helicoi'd with rectilineal generating lines, but with convex generating lines. This is the inevitable result of the fact that the two sides of the grinding wheel inclined at the angle of slope of the fillet are based on'a principle consisting in causing thediamond that cuts the grinding wheel-to describe a combined movement composed on the one hand of a rectilineal displacement along the generating lines of the helicoid, movement carried out in an infinity of planes embracing the zone of contact of the grinding wheel and of the piece-to be wrought, the trajectory of the diamond making with the axis of the latter the angle which corresponds to the generating profile of the thread, and on the other hand of a helical trajectory having the pitch of the thread to be-dressed, described around its axis. The cutting edge of the diamond explores, by this process, the side of the helicoid to be dressed and the'grinding wheel thus gets a profile that fits the helicoid explored by the diamond; it

will thus grind the piece to be wrought with a fillet with rectilineal generating lines.

But this principle has been realised generally in the form of a truing apparatus constituted by an oscillating support intended to be set between the points of the grinding machine and which one couples with its broach; this support carries a diamond mounted on a movable slider making with the axis of the points an angle which one must adjust separately and successively for truing each side of the grinding wheel. Causing the broach of the grinding machine to revolve alternatively forward and backward whilst one operates on the movable slider, one realises in a very imperfect way the principle which has just been exposed.

This realisation is imperfect because on the one hand the inevitable and cumulative plays that always exist in the kinematic chain of pieces causing the movement of the table of the machine in relation with the rotation of its broach have the effect that the helical trajectory of the diamond doubles itself. The diamond describes in fact two helical trajectories, which correspond, each one of them, to one direction of rotation of the broach, and which are set off by the amplitude of these plays which are the play of the reducing gears coupling the guide screw with the broach and the play of the guide screw in its nut and its bearings. The diamond thus cuts the grinding wheel in one direction only and does not touch it in the other.

Another drawback is that, the duration of the contact of the diamond with the grinding wheel being very short, the amplitude of the alternating movement of rotatation of the broach is always much too large, because one cannot.

reverse automatically the march of the table on a very short run. One thus loses a considerable time because the diamond only touches the grinding wheel in a very small fraction of this alternating movement.

A last drawback and probably the worst of this realisation is that the truing apparatus must be mounted between the points, instead and in the position of the piece to be wrought and that, consequently, one cannot true again the grinding wheel without first removing the workpiece and displacing the adjustable head stock of the table by the necessary amount for supporting this truing apparatus. It would be only in a quiteexceptional case, where the workpiece would have the same length as the truing apparatus, that it would not be necessary to displace the adjustable head-stock.

The apparatus which has just been described eliminates all these drawbacks because:

1. It has no play in itsely and cannot take any, for the initial tension of the helical spring 34 presses all the pieces which form the kinematic chain of the movement into one another and absorbs the play of the teeth of the gear 31, of the pinion 38 and of the slider 41; thus, in fact, the diamond always follows the same helical trajectory in one direction as in the other.

'2. It can be placed on the table of the grinding machine, outside of the space comprised between the broach and the adjustable head stock; thus it will not be necessary to remove the work: piece for using it, and the adjustable head stock can always remain in the position which is convenient for the length of the piece.

3. This apparatus'being mounted on the table of the machine, outside of the space reserved for the work-piece, it will suffice, for truing the grinding wheel, to bring the table in a fixed position defined by a stop and in which the apparatus will be facing the grinding wheel.

4. The pitch of the helix to be described by the diamond is adjustable by means of the inclination of the inclined plane 59-59, which forms with the axis of the helicoid an angle, the tangent of which is absolutely proportional to the engendered pitch. The micrometrical screw ll graduated in values of the pitch and operating on the inclined plane permits to effectuate this adjustment without any calculation.

5. In all the other truing apparatuses known, it is necessary to adjust separately, for each side of the grinding wheel, the angle formed by the lineal trajectory of the diamond and the axis of the thread. The described apparatus involves only one angle adjustment and one rotation around the axis of the shaft 22 between the two fixed recesses 26 for truing both sides of the grinding wheel, which is a great simplification for dressing threads with symmetrical profile, which are the most current.

What I claim is:

1. Apparatus for truing a grinding wheel, more particularly a grinding wheel intended for dressing high pitch threads, characterized by a shaft mounted in its bearings in such a way as to be able to rotate and to slide axially, the axis of this shaft being intended to occupy in relation to the grinding wheel the same relative position as the axis of the piece to be ground, by a diamond carried by the shaft and mounted in such a way as to be able to slide parallel with the sides of this grinding wheel, by a supporting plane disposed transversely to the axis of the shaft, by control means enabling to adjust the inclination of this plane in relation with said axis, by a stopping device pressed between the plane and the shaft by means of a spring, and by a mechanism of transmission of movement linking the stopping device to the shaft and such that, when the latter revolves, the device moves along the slope of the supporting plane, the whole in such a way that when one operates the shaft and the diamond, the latter describes a portion of helicoid corresponding to that part of the thread to be dressed which comes in contact with the grinding wheel, the pitch of this helicoid being determined by the inclination of the supporting plane.

2. Apparatus for truing a grinding wheel according to claim 1, characterized in that the above mentioned mechanism of transmission comprises a slider able to move at right angle to the axis of the shaft and linked with the latter by a train of gears, the stopping device being carried by this slider and able to move in respect to it parallel to the said axis.

3. Apparatus for truing a grinding wheel according to claim 1, characterized in that the above mentioned a mechanism of transmission comprises a slider able to move at right angle to the axis of the shaft and linked with the latter by a train of gears, the stopping device comprising at least one roller resting on the inclined plane and the above mentioned spring operating on the shaft and making it rest on another roller of the said device.

4. Apparatus for truing a grinding wheel according to claim 1, characterized in that the control member mentioned in this claim is a micrometrical screw displacing the plane by means of a nut, the travel of which is proportional to the pitch of the fillet of the screw to be dressed.

5. Apparatus for truing a grinding wheel according to claim 1, characterized in that the inclined plane is presented by a piece able to turn around an axis at right angle to that of the shaft.

6. Apparatus for truing a grinding wheel according to claim 1, characterized in that the diamond is mounted on the shaft by means of a support able to turn around an axis at right angle to that of this shaft and to occupy two positions distant of 180, in such a way that by moving the support from one to the other of these positions one causes the diamond to pass from one side of the grinding wheel to the other.

7. Apparatus for truing a grinding wheel ac cording to claim 1, characterized in that the diamond is mounted on the shaft by means of support able to turn around an axis at right angle to that of this shaft and to occupy two positions distant of in such a way that by moving the support from one to the other of these positions one causes the diamond to pass from one side of the grinding wheel to the other, the diamond being mounted on the above mentioned support by means of a head on. which it eifectuates its sliding movement, this head being able to turn around an axis at right angle to those of the support and of the shaft, for the purpose of adapting the sliding direction of the diamond to the angle of the side of the grinding wheel.

8, Apparatus for truing a grinding wheel according to claim 1, characterized in that the diamond is mounted on the shaft by means of a support able to turn around an axis at right angle to that of this shaft and to occupy two positions distant of 180, in such a way that by moving the support from one to the other of these positions one causes the diamond to pass from one side of the grinding wheel to the other, the diamond being mounted on the above mentioned support by means of a head on which it efiectuates its sliding movement, this head being able to turn around an axis at right angle to those of the support and of the shaft, for the purpose of adapting the sliding direction of the diamond to the angle of the side of the grinding wheel, the head carrying two control members for producing the sliding of the diamond, one of which on its upper face and the other on its lower face, in order that one of them be always accessible in the two positions which can be occupied by the head.

FERNAND TURRETTINI. 

